it was mentioned befire that Spark Core doesn’t support IPv6 due to some hardware limitations. It was never fully explained, but I guess main problem was not the wifi module itself, but the amount of rom and ram on the SoC itself to implement proper network stack and still leave space for user application code.
Now with Photon, I think it is worth asking again for IPv6 support.
IPv6 is crucial in enabling cross internet direct connection between devices. This is only way to support millions and billions of devices to cooperate with each other and other like smartphones, laptops, servers. It is impossible or financially viable for devices to be pulled every seconds from central serve. Not only it is slow, it will consume extreme amounts of resources (especially when you include stuff like authentication and encryption). High speed applications (like one Photon communicating something to another Photon with high rate, like 10 times per second) are simply impossible with cloud based solutions. It is also important for reliability, so interconected devices still work even when there is no access to external network or the cloud based systems are offline (we had many examples last years of various minor and major problems, proving that it would be good to be able to work without cloud in some situations).
IPv6 TCP/UDP/ICMP with all usual RA/RD stuff shouldn’t take more than 20KB of ROM space, especially when many things, like HTTP, TCP, UDP and other higher level stuff could be easily shared. There should be almost no RAM memory usage increase. The DNS resolver and other stuff should see no big differences. In case of IPv6-only stack, the memory usage could even decrease, as most likely DHCP client could be just removed.
Things like multicasting or IP mobility are not really necassary in first iteration.
Considering the ROM size increased from 128KB to 1024KB that should be very easy to implement (from the resource point of view).
I am considering buying 10 or even 20 Photons for my own various projects, but without IPv6, I am really not that excited by new hardware.